By means of FEM using ANSYS, this paper set up a three–dimensional model by using Pro/E for model S195 diesel engine’s crankshaft corresponding to practical conditions . The distortion and stress of the crankshaft was investigated . The fatigue strength of crankshaft was verified under changing load . The rationality of crank stress analysis method, which is in current widely used, was discussed . The model analysis was made for the crankshaft , and provide the valuable theory basis for engine design optimizing and improving .